NEW DELHI, India (CNN) -- A 43-year-old woman convicted in the assassination of former Indian prime minister Rajiv Gandhi is on a hunger strike to seek her early release from jail, a prison official said.

A plotter in the death of Rajiv Gandhi has begun a hunger strike to seek early release from jail.

Nalini Sriharan has been in jail 18 years, said Jaya Bharathi, superintendent of Vellore prison.

Sriharan was convicted of plotting the murder of Gandhi in a suicide bomb attack in 1991. She received a death sentence along with her husband and two others.

Sriharan's sentence was commuted to life imprisonment on a mercy petition by Sonia Gandhi, the Italian-born widow of the slain former prime minister.

The other three remain on death row.

In India, a lifer becomes eligible for early release after serving 14 years, Bharathi said.

Sriharan is demanding that a decision be made on setting her free.

"It's a second day of her indefinite fast," Bharathi said.

India accused Sri Lanka's Tamil rebels of ordering the murder of Gandhi, who had sent Indian peacekeepers to the restive island nation while in power.